The commissioner requested I notate 'that there is an illustration that perfectly matches the story, available on e621.net by VSDrawFag'. It's an (obviously NSFW) companion image to this chapter specifically. I can't post a direct link to it, but I can do this: https://derpiboo.org/ 1307111.

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Pound's moaned out as the new sensations rocked through his body, Flurry's flaps sliding down him instead of him into her, his flare popping past them and inside of her filly-parts again. A warm, insistent, squeezing inside-hug on his pee-pee greeted him as he passed deeper, feeling Flurry's insides gripping on him, with that feeling being so instinctively perfect to the young stallion. "Y-Your...part's squeezing mine...is...that you doing that?" he asked, confused at the new feelings her being on top added.

"I...I don't know...this feels..." Flurry commented, only giving a hard shudder atop him in conclusion. As she rose her hips, as she'd observed her mother Cadence do when she and her father Shining Armor had done this together, she then quickly dropped on him, finding that it didn't hurt this time, instead feeling amazing. "T-That..." Flurry muttered out, before repeating that drop just as hard, again and again.

Pound's tongue slid out of his mouth as he started panting, the feeling of her inside place on his willy so amazingly awesome he never wanted it to stop. When he, however, started rocking his hips up to meet her drops, impeding her at first before getting into her rhythm, he found it felt even more amazing than when he held still and let her do everything. Each hump up made her drop feel more...validated somehow; as though he was confirming that, yes, they were doing this right now.

Flurry, on the other hoof, welcomed the feeling of Pound living up to his name, pounding up into her midway of each drop, adding force to each stop and making her lower lips slap wetly against his ring. Both foals were speechless, their bodies simply running on their hard-wired instinct to reproduce, every fiber of their beings screaming this was right; that this was what sexually-mature fillies and colts were supposed to do together this time of year, in order to assure that there would be more fillies and colts born next year.

While it used to hurt when Pound hit that deepest portion of her, Flurry found that now it felt more comfortable than a hug on a cold winter day. Each time he hit it made the feelings spike a little more for Flurry, the squishing, schlicking sounds of their breeding grew louder as their pace increased. She felt her little bump thingy poking out rapidly now, feeling the wetness her marehood was releasing to help him slide that much easier.

Seeing her teats poking out more in her arousal, Pound started to softly rub them with a hoof, earning a quiet moan from Flurry. He also quickly felt the bulge he was leaving in her as his stallionhood spread her wide, making him shudder as he remembered it was indeed him who was doing that to her, and while he wasn't sure why, he LOVED that.

Meanwhile, while Flurry was riding her colt brother like the stallion he now was, Pumpkin was using both hooves to stimulate her fillyhood, watching Pound and Flurry doing this making the urge to touch herself 'down there' impossible to resist. She felt her own pleasure rising up, though her hooves weren't enough. Soon she lit her horn and started rubbing with her magic instead, letting a quiet squeal at the intense, tingling sensations that manipulation spell added.

Flurry meanwhile trailed a hoof down to touch where Pound and she met and separated so intimately, feeling the same bulge he had, and for some reason that made her shudder hard at the fact that he was in her filly-place, stretching her so far, making her feel good on a very deep level. Like she was supposed to have him stretching her open so much in there, and more.

This went on for a minute or so, Pound and Flurry unsteadily rocking against each other, Flurry grinding against his thick medial ring when he was deep inside her and finding that it felt absolutely indescribable when her pleasure nub came out and hit it. Flurry felt a kind of pressure and heat building where Pound's thick tip was, completely oblivious to everything else except that growing sensation and Pound's member in her belly. It didn't hurt though, quite the opposite. Her body was screaming at her that this was the best thing ever, to keep rocking her hips like she was. She only too eagerly did.

Pound felt that same pressure building in his pelvis as he had the previous night when he'd 'milked', his hips starting to lose the rhythm as he felt the urge, the overwhelming need, to get as deep inside of Flurry as he could and stay there, yet not knowing why. He felt his tip getting bigger again, the sensations in his groin rapidly increasing alongside his pulses growing more rapid and rhythmic.

"I'm...I'm gonna milk...s-soon..." Pound muttered, struggling to stay inside Flurry's hole as she increased her pace again. Needing to stay inside of her, he yanked down hard with his hooves around her croup and hips, forcing her to keep his member as deep as she could as his instincts demanded he do, them telling him something very important was about to happen, and he needed to stay as far as possible inside her when it did.

"F-Flurry, it feels like I need to...p-peeeee!" Pound warned, though he knew somehow that it wouldn't be pee coming from him. He was pretty sure it would be that milk stuff, and he felt he needed to do it inside her for some reason.

Flurry was too far gone and didn't hear Pound's warning, then yelped as she felt herself being yanked down and felt his thingy getting bigger and throbbing very deep inside of her, her passage in turn squeezing rapidly on him in response, the pressure and heat building up even higher for her. "P-Pound, I...I feel..." she stammered out, feeling the pressure and powerful feelings magnifying in her belly as he grew bigger in her and spread her depths more. She'd never felt something so intensely as she was now, her whole body needing to get rid of this pressure, feeling like she was about to explode, and on some level she knew she would, in a sense.

Pumpkin watched from the sidelines as Pound and Flurry reached their penultimate moment, her own sensations starting to accumulate quickly. "W-wow..." she simply muttered as she watched her brother holding Flurry tight to him, seeing the base of his thingy throbbing, the rest deep inside her, his ball-things flexing in time, tail flagged aside to show his sister everything. As the other two cried out simultaneously, Pumpkin rubbed her nub rapidly as it peeked out, that final spike of stimulation sending her rocketing over with them.

Pound felt as his thingy started pulsing hard inside of Flurry against his will, tail slightly flagging with each pump, intense waves of pleasure rolling through him. He felt something shooting out of him and into Flurry with each throb, his hips rocking against her with each thick ejaculation. Pound’s tip was pressed taut against what he didn't know was her cervix, sending his virile load directly into her small, immature womb as his thick flare let nothing past.

As Flurry felt something very thick, warm, and sticky shooting and pooling deep into her belly as Pound's penis throbbed inside of her, for some reason that was the best thing she'd ever felt in her life – followed instantly by the new best thing she'd felt in her entire life. Flurry cried out the same time as Pound did as she felt her insides start to squeeze Pound hard from base to swollen tip, feeling intimately each throb it made inside of her, each shot of cum he gushed deeply into her, all topped off by intense tingles rolling through her. She couldn't think, could hardly breathe, her whole focus being on keeping that stallionhood deep inside her marehood, pumping that warmth she really liked into her belly, making it swell up a bit.

Flurry felt something oozing from her, something thick gushing out of her and onto the colt beneath her. Releasing her own off-white mare-cum to mix with Pound's semen, rolling down his sides while her bump blinked rapidly against his ring and only added to the sensations that much more. As she remembered something else her parents did when they were doing this, Flurry leaned over and met her lips with Pound's, giving the young stallion the first, sloppy, kiss of his life.

Pound felt a wetness released on his crotch and pee-pee, passively wondering if Flurry was peeing on him, but that thought was instantly washed away with another squirt of his seed deep within her and the accompanying surge of ecstasy. As he felt Flurry's lips meet his, he was initially very surprised, but instead moaned into her muzzle as he pressed back, finding that her kissing him was only enhancing the sensations already rolling through him.

Pumpkin meanwhile felt her own first orgasm rocking through her, her hoof digging at her bump that was constantly 'blinking' now. She felt her whole hoof getting soaked with her off-white-tinted fluids and some even squirting past to get on her brother's cheek as she jerked her hips rapidly against it on instinct, rubbing along her whole slit with the frog of her hoof. The feeling was so intense, but her body felt it was missing something, making her wonder if it could feel even better than this. Her fillyhood felt so empty for some reason, and she couldn't understand why...until she looked over at the other two foals and again saw Pound's thingy pulsing deep inside of Flurry. Maybe...

As the trio slowly came off their highs, none knowing just what had happened, Flurry collapsed onto Pound, laying atop him now as the three rested, his thingy still all big inside of her and the building heat and pressure she’d been feeling before dissipated. Eventually Pound's member softened and slid out of Flurry with a quiet 'schlick', both moaning as they felt it. "W-What was...that?" Flurry asked, a little scared and confused at what she'd just felt, "It felt...weird but good. Like my...insides were really hugging you? Then I was tingly all over and...I couldn't stop it and...then it felt like I...peed on you?"

"Yeah...that's what it feels like when my milk comes out, except it's more like...my pee-pee pulses then milk comes out. I...I don't smell pee either, just more of that...clear stuff you made earlier? But it smells different."

"Oh, it's not pee? Phew. Was that...your 'milk' I felt...going in me...?"

"I think so..."

"Wow...it feels really good and warm inside my tummy now."

"Yeah, felt really good when I put it there too..."

Pumpkin was meanwhile watching from behind as her brother's willy popped out of Flurry, watching the milky mess go out of her and onto Pound's ball-things and tail, joining Flurry's 'fluids that weren't pee'. "Wow...it really does look like milk, except it's a lot thicker looking...and smells different." she muttered, then she got something in her mind, "Hey bro, do you think you could do that to m—"

"POUND, PUMPKIN, FLURRY, IT'S TIME FOR LUNCH! GET YOUR HOOVES CLEANED AND COME EAT!" Pinkie's cheery voice called up, startling the trio.

"C'mon, let's go take a bath really quick. We can't go down there like this..." Pound said, gently rolling Flurry off of him as he stood, smelling like two satisfied mares.

"But Pound... I wanted..." Pumpkin said, unable to hide her disappointment.

"Don't worry sis, we can always do this more later. Next time, you can go first!"

Both filly and young mare couldn't hide their enthusiasm at that promise.

Author's Note

...and done. Hope you liked this story!

Another thanks to 'Frost' for the commission! I hope you all enjoyed!

If you'd like me to write for you as well, please check my blog post on commissioning me for how to do so.

Until next time, I'll see you all in the comments section or my next story. Au revoir et à bientôt!!